Mercurial > repos > shellac > sam_consensus_v3
diff env/lib/python3.9/site-packages/networkx/algorithms/wiener.py @ 0:4f3585e2f14b draft default tip
"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author | shellac |
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date | Mon, 22 Mar 2021 18:12:50 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/env/lib/python3.9/site-packages/networkx/algorithms/wiener.py Mon Mar 22 18:12:50 2021 +0000 @@ -0,0 +1,77 @@ +"""Functions related to the Wiener index of a graph.""" + +from itertools import chain + +from .components import is_connected +from .components import is_strongly_connected +from .shortest_paths import shortest_path_length as spl + +__all__ = ["wiener_index"] + +#: Rename the :func:`chain.from_iterable` function for the sake of +#: brevity. +chaini = chain.from_iterable + + +def wiener_index(G, weight=None): + """Returns the Wiener index of the given graph. + + The *Wiener index* of a graph is the sum of the shortest-path + distances between each pair of reachable nodes. For pairs of nodes + in undirected graphs, only one orientation of the pair is counted. + + Parameters + ---------- + G : NetworkX graph + + weight : object + The edge attribute to use as distance when computing + shortest-path distances. This is passed directly to the + :func:`networkx.shortest_path_length` function. + + Returns + ------- + float + The Wiener index of the graph `G`. + + Raises + ------ + NetworkXError + If the graph `G` is not connected. + + Notes + ----- + If a pair of nodes is not reachable, the distance is assumed to be + infinity. This means that for graphs that are not + strongly-connected, this function returns ``inf``. + + The Wiener index is not usually defined for directed graphs, however + this function uses the natural generalization of the Wiener index to + directed graphs. + + Examples + -------- + The Wiener index of the (unweighted) complete graph on *n* nodes + equals the number of pairs of the *n* nodes, since each pair of + nodes is at distance one:: + + >>> n = 10 + >>> G = nx.complete_graph(n) + >>> nx.wiener_index(G) == n * (n - 1) / 2 + True + + Graphs that are not strongly-connected have infinite Wiener index:: + + >>> G = nx.empty_graph(2) + >>> nx.wiener_index(G) + inf + + """ + is_directed = G.is_directed() + if (is_directed and not is_strongly_connected(G)) or ( + not is_directed and not is_connected(G) + ): + return float("inf") + total = sum(chaini(p.values() for v, p in spl(G, weight=weight))) + # Need to account for double counting pairs of nodes in undirected graphs. + return total if is_directed else total / 2